Count Twin Primes

You are given an integer n. Your task is to count the number of twin prime pairs, where a twin prime pair is defined as two prime numbers \(p\) and \(q\) such that \(q - p = 2\) and \(q \le n\). For example, the pair (3, 5) is a twin prime because both 3 and 5 are prime, and \(5 - 3 = 2\).

Input: A single integer n from standard input.

Output: Output a single integer representing the number of twin prime pairs \((p, q)\) satisfying the conditions.

Example:

Input: 10
Output: 2

inputFormat

The input consists of a single integer n (\(n \ge 2\)). This integer is provided via standard input.

outputFormat

Output a single integer to standard output, which is the number of twin prime pairs \((p, q)\) such that \(q - p = 2\) and \(q \le n\).

10

2